Ultra low k plasma enhanced chemical vapor deposition processes using a single bifunctional precursor containing both a SiCOH matrix functionality and organic porogen functionality

ABSTRACT

A method for fabricating a SiCOH dielectric material comprising Si, C, O and H atoms from a single organosilicon precursor with a built-in organic porogen is provided. The single organosilicon precursor with a built-in organic porogen is selected from silane (SiH 4 ) derivatives having the molecular formula SiRR 1 R 2 R 3 , disiloxane derivatives having the molecular formula R 4 R 5 R 6 —Si—O—Si—R 7 R 8 R 9 , and trisiloxane derivatives having the molecular formula R 10 R 11 R 12 —Si—O—Si—R 13 R 14 —O—Si—R 15 R 16 R 17  where R and R 1-17  may or may not be identical and are selected from H, alkyl, alkoxy, epoxy, phenyl, vinyl, allyl, alkenyl or alkynyl groups that may be linear, branched, cyclic, polycyclic and may be functionalized with oxygen, nitrogen or fluorine containing substituents. In addition to the method, the present application also provides SiCOH dielectrics made from the inventive method as well as electronic structures that contain the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to co-assigned U.S. Pat. Nos.6,147,009, 6,312,793, 6,441,491, 6,437,443, 6,541,398, 6,479,110 B2 and6,497,963, the entire contents of each of the aforementioned U.S.patents are incorporated herein by reference. The present application isalso related to the following co-pending and co-assigned U.S. patentapplications Ser. No. 10/174,749, filed Jun. 19, 2002, Ser. No.10/340,000, filed Jan. 23, 2003, Ser. No. 10/390,801, filed Mar. 18,2003, and Ser. No. 10/758,724, filed Jan. 16, 2004. The contents of eachof the aforementioned U.S. Patent Applications are also incorporatedherein by reference in their entirety as well.

FIELD OF THE INVENTION

The present invention generally relates to a method of fabricating adielectric material that has an ultralow dielectric constant (orultralow k) using a plasma enhanced chemical vapor deposition (PECVD)process in which a single organosilicon precursor containing a built-inorganic porogen is employed as well as a method of fabricatingelectronic devices containing such a dielectric material. The use of asingle precursor in a PECVD process enables easier control of theprocess, better control of film thickness and compositional uniformityand simplifies the manufacturing process. Moreover, the deposition of adielectric film from a single precursor enables better control of thefinal porosity in the film and a narrower pore size distributionresulting in better mechanical properties at the same value ofdielectric constant.

More particularly, the present invention relates to a method offabricating a thermally stable ultralow k dielectric film for use as anintralevel or interlevel dielectric in an ultra large scale integration(ULSI) back-end-of-the-line (BEOL) wiring structure and an electronicstructure formed by such a method.

BACKGROUND OF THE INVENTION

The continuous shrinking in dimensions of electronic devices utilized inULSI circuits in recent years has resulted in increasing the resistanceof the BEOL metallization as well as increasing the capacitance of theintralayer and interlayer dielectric. This combined effect increasessignal delays in ULSI electronic devices. In order to improve theswitching performance of future ULSI circuits, low dielectric constant(k) insulators and particularly those with k significantly lower thansilicon oxide are needed to reduce the capacitances. Dielectricmaterials (i.e., dielectrics) that have low k values are commerciallyavailable. One such commercially available material, for example, ispolytetrafluoroethylene (“PTFE”), which has a dielectric constant ofabout 2.0. Most commercially available dielectric materials however arenot thermally stable when exposed to temperatures above 300° C.Integration of low k dielectrics in present ULSI chips requires athermal stability of at least 400° C.

The low k materials that have been considered for applications in ULSIdevices include polymers containing elements of Si, C, O and H, such asmethylsiloxane, methylsilsesquioxanes, and other organic and inorganicpolymers. For instance, an article by N. Hacker et al. “Properties ofnew low dielectric constant spin-on silicon oxide based dielectrics”Mat. Res. Soc. Symp. Proc. 476 (1997): 25 describes materials thatappear to satisfy the thermal stability requirement, even though some ofthese materials propagate cracks easily when reaching thicknesses neededfor integration in an interconnect structure when films are prepared bya spin-on technique. Furthermore, these prior art precursor materialsare high cost and prohibitive for use in mass production. Moreover, mostof the fabrication steps of very large scale integration (“VLSI”) andULSI chips are carried out by plasma enhanced chemical or physical vapordeposition techniques.

The ability to fabricate a low k material by a plasma enhanced chemicalvapor deposition (PECVD) technique using previously installed andavailable processing equipment will thus simplify its integration in themanufacturing process, reduce manufacturing cost, and create lesshazardous waste. U.S. Pat. Nos. 6,147,009 and 6,497,963 describe a lowdielectric constant material consisting of elements of Si, C, O and Hatoms having a dielectric constant of not more than 3.6 and whichexhibits very low crack propagation velocities.

U.S. Pat. Nos. 6,312,793, 6,441,491, 6,541,398 and 6,479,110 B2 describea multiphase low k dielectric material that consists of a matrix phasecomposed of elements of Si, C, O and H and another phase composed mainlyof C and H. The dielectric materials disclosed in the foregoing patentshave a dielectric constant of not more than 3.2.

U.S. Pat. No. 6,437,443 describes a low k dielectric material that hastwo or more phases wherein the first phase is formed of a SiCOHmaterial. The low k dielectric material is provided by reacting a firstprecursor gas containing atoms of Si, C, O, and H and at least a secondprecursor gas containing mainly atoms of C, H, and optionally F, N and Oin a plasma enhanced chemical vapor deposition chamber.

Despite the numerous disclosures of low k dielectric materials, there isa continued need to improve the PECVD process in order to improve theproperties of the final SiCOH dielectric material. For example, a SiCOHdielectric material having a lower internal stress, improved thermalstability, lower cost and better process control within processingtemperatures used in current ULSI technologies are all needed.

It is commonly found that SiCOH dielectric materials made in the priorart from two or more separate organosilicon and/or porogen precursorsare not uniform in atomic and structural composition, both when measuredacross the substrate diameter, and through the depth of the layer. Theuse of 300 mm Si wafers has made this problem of chemical uniformityacross the wafer more pronounced.

It is also commonly found that SiCOH dielectric materials made from twoor more separate organosilicon and/or porogen precursors exhibit processvariation or process instability due to small changes in the flow rateof one of the two precursors, known as drift in the flow rate.

In view of the above, there is a need to provide a process to fabricatea layer of a SiCOH dielectric material having improved film properties,that is uniform in atomic and structural composition, both when measuredacross the substrate diameter, and through the depth of the layer, whichdoes not exhibit any variation in the process or process instability.

SUMMARY OF THE INVENTION

The present invention provides a method for fabricating a dielectricmaterial having a dielectric constant of not more than about 2.7 from asingle organosilicon precursor with a built-in organic porogen. Morepreferably, the dielectric constant of the ultralow k material of thepresent invention is from about 1.5 to about 2.6, and most preferably,the dielectric constant is from about 1.8 to 2.5. All dielectricconstants mentioned in the present application are relative to a vacuumunless otherwise specified.

The present invention also provides a method for fabricating a SiCOHdielectric material comprising Si, C, O and H atoms from a singleorganosilicon precursor with a built-in organic porogen. The singleorganosilicon precursor with a built-in organic porogen is selected fromsilane (SiH₄) derivatives having the molecular formula SiRR¹R²R³,disiloxane derivatives having the molecular formulaR⁴R⁵R⁶Si—O—Si—R⁷R⁸R⁹, and trisiloxane derivatives having the molecularformula R¹⁰R¹¹R¹²—Si—O—Si—R¹³R¹⁴—O—Si—R¹⁵R¹⁶R¹⁷ where R and R¹⁻¹⁷ may ormay not be identical and are selected from H, alkyl, alkoxy, epoxy,phenyl, vinyl, allyl, alkenyl or alkynyl groups that may be linear,branched, cyclic, polycyclic and may be functionalized with oxygen,nitrogen or fluorine containing substituents.

Specifically, the present invention provides a PECVD process forfabricating a layer of a SiCOH dielectric material having improved filmproperties, that is uniform in atomic and structural composition, bothwhen measured across the substrate diameter, and through the depth ofthe layer, which does not exhibit variation in the process or processinstability.

By “uniform in atomic composition”, it is meant that the dielectricmaterial has a substantially constant atom distributed throughout thefilm in both the vertical and horizontal direction. By “uniform instructural composition”, it is meant a substantially constantarrangement of atoms within the film in both the vertical and horizontaldirections.

The use of a single organosilicon precursor in a PECVD process enableseasier control of the process, better control of film thickness andcompositional uniformity and simplifies the manufacturing process.Furthermore, the deposition of a film from a single organosiliconprecursor enables better control of the final porosity in the film and anarrower pore size distribution, potentially resulting in bettermechanical properties at the same values of dielectric constant.Furthermore, the deposition of a film from a single organosiliconprecursor enables better control of the mechanical properties of thefinal SiCOH dielectric because the bonding in the final film is closelyrelated to the bonding in the single organosilicon precursor with abuilt-in organic porogen.

In broad terms, the method (or process) of the present inventioncomprises the steps of:

positioning a substrate in a PECVD reactor;

providing a single organosilicon precursor with a built-in organicporogen into said PECVD reactor, said single organosilicon precursorwith a built-in organic porogen comprising a silane derivative havingthe molecular formula SiRR¹R²R³, a disiloxane derivative having themolecular formula R⁴R⁵R⁶—Si—O—Si—R⁷R⁸R⁹, or a trisiloxane derivativehaving the molecular formula R¹⁰R¹¹R¹²Si—O—Si—R¹³R¹⁴—O—Si—R¹⁵R¹⁶R¹⁷where R and R¹⁻¹⁷ may or may not be identical and are selected from H,alkyl, alkoxy, epoxy, phenyl, vinyl, allyl, alkenyl or alkynyl groupsthat may be linear, branched, cyclic, polycyclic and may befunctionalized with oxygen, nitrogen or fluorine containingsubstituents;

forming an as deposited film from said single organsilicon precursor,said as deposited film comprising a SiCOH matrix component and anorganic porogen component; and

performing a treatment step that substantially removes said organicporogen component from said as deposited film thereby providing a SiCOHdielectric material having a dielectric constant of about 2.7 or lower.

In addition to the method described above, the present invention alsoprovides a SiCOH dielectric film which is prepared using the methoddescribed above. Specifically, the dielectric film of the presentinvention comprises a dielectric material comprising atoms of Si, C, Oand H, said dielectric material having a covalently bondedtri-dimensional network structure, a dielectric constant of not morethan 2.7, a controlled porosity having molecular scale voids from about0.5 to about 20 nanometers in diameter, and preferably from about 0.5 toabout 5 nm in diameter. According to the invention, the molecular scalevoids occupy a volume of between about 5% and about 60%. Also accordingto the invention, the dielectric material of this invention containsmolecular scale voids that are characterized by a pore size distributionand said size distribution has a maximum (in the distribution) between0.7 and 3 nm, and preferably between 0.7 and 2.5 nm.

The present invention also relates to electronic structures that includeat least one insulating material that comprises the SiCOH dielectricfilm of the present invention. The at least one dielectric filmcomprising the inventive SiCOH dielectric may comprise an interleveland/or intralevel dielectric layer, a capping layer, and/or a hardmask/polish-stop layer in an electronic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are pictorial representations (through cross sectionalviews) illustrating the basic processing steps of the present invention.

FIG. 2 is an enlarged, cross-sectional view of an electronic device ofthe present invention that includes the inventive SiCOH dielectric filmas both the intralevel dielectric layer and the interlevel dielectriclayer.

FIG. 3 is an enlarged, cross-sectional view of the electronic structureof FIG. 2 having an additional diffusion barrier dielectric cap layerdeposited on top of the inventive SiCOH dielectric film.

FIG. 4 is an enlarged, cross-sectional view of the electronic structureof FIG. 3 having an additional RIE hard mask/polish-stop dielectric caplayer and a dielectric cap diffusion barrier layer deposited on top ofthe polish-stop layer.

FIG. 5 is an enlarged, cross-sectional view of the electronic structureof FIG. 4 having additional RIE hard mask/polish-stop dielectric layersdeposited on top of the SiCOH dielectric film of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, which describes a method of fabricating a SiCOHdielectric material using a single organosilicon precursor containing abuilt-in organic porogen, a SiCOH dielectric film formed by theinventive method and electronic structures containing the same, will nowbe described in greater detail.

In accordance with the method of the present invention, an as depositeddielectric film 12 is formed on a surface of a substrate 10 such asshown, for example, in FIG. 1A. The term “substrate” when used inconjunction with substrate 10 includes, a semiconducting material, aninsulating material, a conductive material or any combination thereof,including multilayered structures. Thus, for example, substrate 10 canbe a semiconducting material such as Si, SiGe, SiGeC, SiC, GaAs, InAs,InP and other III/V or II/VI compound semiconductors. The semiconductorsubstrate 10 can also include a layered substrate such as, for example,Si/SiGe, Si/SiC, silicon-on-insulators (SOIs) or silicongermanium-on-insulators (SGOIs). When substrate 10 is an insulatingmaterial, the insulating material can be an organic insulator, aninorganic insulator or a combination thereof including multilayers. Whenthe substrate 10 is a conductive material, the substrate 10 may include,for example, polySi, an elemental metal, alloys of elemental metals, ametal silicide, a metal nitride and combinations thereof, includingmultilayers.

In some embodiments, the substrate 10 includes a combination of asemiconducting material and an insulating material, a combination of asemiconducting material and a conductive material or a combination of asemiconducting material, an insulating material and a conductivematerial. An example of a substrate that includes a combination of theabove is an interconnect structure.

The as deposited dielectric film 12 is formed in the present inventionutilizing a plasma enhanced chemical vapor deposition (PECVD) reactor inwhich a single organosilicon precursor containing a built-in organicporogen is employed. The thickness of the as deposited dielectric film12 may vary; typical ranges for the deposited dielectric film 12 arefrom about 50 nm to about 1 μm, with a thickness from 100 to about 500nm being more typical.

Typically, the dielectric film 12 is deposited using the processingtechniques disclosed in co-assigned U.S. Pat. Nos. 6,147,009, 6,312,793,6,441,491, 6,437,443, 6,441,491, 6,541,398, 6,479,110 B2, and 6,497,963,the contents of which are incorporated herein by reference, with theexception that a single organosilicon precursor containing a built-inorganic porogen (to be described in greater detail herein below) isemployed.

Specifically, the as deposited dielectric film 12 is formed by providingthe single organosilicon precursor containing a build-in organic porogenand an optional inert carrier such as He, Ne, or Ar, into a reactor,preferably the reactor is a PECVD reactor, and then depositing a filmderived from said precursor onto a suitable substrate utilizingconditions that are effective in forming a dielectric material. Thesubstrate is positioned within the PECVD reactor on top of a substrateholder. The present invention yet further provides for mixing theprecursor with an oxidizing agent such as O₂, CO₂ or a combinationthereof, thereby stabilizing the reactants in the reactor and improvingthe uniformity of the dielectric film 12 deposited on the substrate 10.

The single organosilicon precursor with a built-in organic porogen isselected from silane (SiH₄) derivatives having the molecular formulaSiRR¹R²R³, disiloxane derivatives having the molecular formulaR⁴R⁵R⁶—Si—O—Si—R⁷R⁸R⁹, and trisiloxane derivatives having the molecularformula R¹⁰R¹¹R¹²Si—O—SiR¹³R¹⁴—O—Si—R¹⁵R¹⁶R¹⁷ where R and R¹⁻¹⁷ may ormay not be identical and are selected from H, alkyl, alkoxy, epoxy,phenyl, vinyl, allyl, alkenyl or alkynyl groups that may be linear,branched, cyclic, polycyclic and may be functionalized with oxygen,nitrogen or fluorine containing substituents.

Preferred single organosilicon precursor with a built-in organic porogeninclude, but are not limited to: allylazadimethoxysilacyclopentane,allylaminopropyltrimethoxysilane, allyldimethoxysilane,allyldimethylsilane, allyloxy-t-butyldimethylsilane,allyloxytrimethylsilane, allyltetramethyldisiloxane,allyltriethoxysilane, allyltrimethoxysilane,bicycloheptenylethyltrimethoxysilane, bicycloheptenyltriethoxysilane,bisallyloxymethyltrimethylsiloxybutane,bisbicycloheptenylethyltetramethyldisiloxane,bisepoxycyclohexylethyltetramethyldisiloxane,bistrimethylsiloxycyclobutene, bis(trimethoxysilyl)ethane,bis(trimethoxysilyl)decane, bis(trimethoxysilyl)hexane,butenyltriethoxysilane, butenyltrimethylsilane,(t-butyldimethylsiloxy)butyne, cyclohexenylethyltriethoxysilane,cyclohexenyltrimethoxysilane, cyclohexyltrimethoxysilane,cyclopentadienylpropyltriethoxysilane, cyclopenenyloxytrimethylsilane,cyclopentyltrimethoxysilane, diallyltetramethyldisiloxane,diethoxysilacyclopentene, diethyldiethoxysilane, dimethyldiethoxysilane,dimethyldimethoxysilane, dimethylbutylideneaminopropyltriethoxysilane,dimethylsilaoxacyclohexane, divinyldiphenyldimethyldisiloxane,divinyldiphenyltetramethyldisiloxane, divinyltetraphenyldisiloxane,2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,5,6-epoxyhexyltriethoxysilane, propargyloxytrimethylsilane,divinyltetramethyldisiloxane, divinyldimethylsilane,hexavinyldisiloxane, hexaphenyldisiloxane, di-tert-butyldimethoxysilane,hexamethyltrisiloxane, hexamethylcyclotrisiloxane,methyltriethoxysilane, methyltrimethoxysilane, octeyltrimethoxysilane,octenyldimethylsilane, octyltrimethoxysilane, propenyltrimethylsilane,tetraallylsilane, tetramethyldisiloxane, tetravinyldimethyldisiloxane,tetravinylsilane, trimethylsilylcyclopentene,

trivinylcyclotrisiloxane, trivinyltrisiloxane,trivinyltrimethylcyclotrisiloxane, trivinylpentamethyltrisiloxane,glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldiethoxysilane,tetraethoxydimethyldisiloxane, tetraisopropyldisiloxane,trivinylmethoxysilane, trivinylethoxysilane, trivinylsilane,vinyldimethylethoxysilane, vinylmethyldiethoxysilane,vinylmethyldimethoxysilane, vinylmethylethoxysilane,vinylmethyldiethoxysilane, vinylmethyldimethoxysilane,vinylpentamethyldisiloxane, vinyltetramethyldisiloxane,vinyltri-t-butoxysilane, vinyltriethoxysilane,vinyltriisopropenoxysilane, vinyltriisopropoxysilane,vinyltrimethoxysilane ethoxytrimethylsilane, ethoxydimethylsilane,dimethoxydimethylsilane, dimethoxymethylsilane, triethoxysilane, andtrimethoxymethylsilane.

In a preferred embodiment, the organosilicon precursor with a built-inorganic porogen is vinylmethyldiethoxysilane, vinyltriethoxysilane,vinyldimethylethoxysilane, cyclohexenylethyltriethoxysilane,1,1-diethoxy-1-silacyclopent-3-ene, divinyltetramethyldisiloxane,2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, epoxyhexyltriethoxysilane,hexavinyldisiloxane, trivinylmethoxysilane, trivinylethoxysilane,vinylmethylethoxysilane, vinylmethyldiethoxysilane,vinylmethyldimethoxysilane, vinylpentamethyldisiloxane,vinyltetramethyldisiloxane, vinyltriethoxysilane, orvinyltrimethoxysilane.

The as deposited dielectric film 12 may be deposited using a method theincludes the step of providing a parallel plate reactor, which has aconductive area of a substrate chuck between about 85 cm² and about 750cm², and a gap between the substrate and a top electrode between about 1cm and about 12 cm. A high frequency RF power is applied to one of theelectrodes at a frequency between about 0.45 MHz and about 200 MHz.Optionally, an additional low frequency power can be applied to one ofthe electrodes.

The conditions used for the deposition step may vary depending on thedesired final dielectric constant of the dielectric film. Broadly, theconditions used for providing a stable dielectric material comprisingelements of Si, C, O, H that has a dielectric constant of about 2.7 orless include: setting the substrate temperature at between about 200° C.and about 425° C.; setting the high frequency RF power density atbetween about 0.1 W/cm² and about 2.5 W/cm²; setting the singleorganosilicon precursor flow rate at between about 100 mg/min and about5000 mg/min, optionally setting the inert carrier gases such as helium(and/or argon) flow rate at between about 50 sccm to about 5000 sccm;and setting the reactor pressure at a pressure between about 1000 mTorrand about 10000 mTorr. Optionally, a low frequency power may be added tothe plasma between about 30 W and about 400 W. Note that the RF powermay be replaced with another energy source which is also capable ofdissociating the precursor. For organosilicon gas precursors, the flowrate is between about 20 sccm to about 3000 sccm with the same reactorpressure between about 1000 mTorr and about 10000 mTorr.

When an oxidizing agent is employed in the present invention, it isflown into the PECVD reactor at a flow rate between about 10 sccm toabout 1000 sccm.

While a parallel plate PECVD reactor is specifically mentioned above,the as deposited dielectric film 12 can be deposited from a high densityplasma reactor.

The dielectric film 12 formed at this point of the present invention iscomprised of two components. The first component is a SiCOH matrix andthe second component is the organic porogen. The organic porogencomponent is interconnected with the SiCOH matrix. The SiCOH matrix iscomprised of a hydrogenated oxidized silicon carbon material (SiCOH)comprising atoms of Si, C, O and H in a covalently bondedtri-dimensional network and having a dielectric constant of not morethan about 2.8. The tri-bonded network may include a covalently bondedtri-dimensional ring structure comprising Si—O, Si—C, Si—H, C—H and C—Cbonds. More preferably, the dielectric constant of the as deposited film12 is from about 1.5 to about 2.6, and most preferably from about 1.8 toabout 2.5.

The SiCOH matrix of the as deposited dielectric film 12 comprisesbetween about 5 and about 40 atomic percent of Si; between about 5 andabout 45 atomic percent of C; between 0 and about 50 atomic percent ofO; and between about 10 and about 55 atomic percent of H.

After forming the as deposited dielectric film 12 on the substrate 10,the structure shown, for example, in FIG. 1A is subjected to a treatmentstep that is capable of substantially removing the organic porogencomponent from the as deposited film 12 thereby forming a SiCOHdielectric material 14 having a dielectric constant that is not greaterthan 2.7, preferably from about 1.5 to about 2.6, and more preferablyfrom about 1.8 to about 2.5. The structure formed after this treatmentstep has been performed is shown, for example, in FIG. 1B. Note that thedielectric constant of the SiCOH dielectric material 14 after thistreatment step is slightly less than the original dielectric constant ofthe as deposited dielectric film 12.

The treatment step described herein can be implemented after a singlelayer deposition or after several deposition steps (multi layerdeposition).

The treatment step performed at this point of the present inventionrequires sufficient energy to break the organic porogen componentpresent in the as deposited dielectric film 12 from the SiCOH matrix andto remove the porogen from the final film 14. The energy source used forthe dissociation may be thermal, electron beam, plasma or opticalradiation such as UV or laser. Combinations of the aforementioned energysources can also be used in the present invention. The removal of theorganic porogen is typically associated with additional cross linking ofthe film.

The thermal energy source includes any source such as, for example, aheating element or a lamp, that can heat the deposited dielectricmaterial to a temperature up to 450° C. More preferably, the thermalenergy source is capable of heating the deposited dielectric material toa temperature from about 200° to about 450° C., with a temperature fromabout 350° C. to about 425° C. being even more preferred. This thermaltreatment process can be carried out for various time periods, with atime period from about 0.5 minutes to about 300 minutes being typical.The thermal treatment step is typically performed in the presence of aninert gas such as He, Ar, Ne, Xe, N₂ or a mixture thereof. The thermaltreatment step may be referred to as an anneal step in which rapidthermal anneal, furnace anneal, laser anneal or spike anneal conditionsare employed.

In some embodiments, the thermal treatment step can be performed in thepresence of a gas mixture containing a hydrogen source gas such as, forexample, H₂ or a hydrocarbon. In yet other embodiments, the thermaltreatment step can be performed in the presence of a gas mixturecontaining a very low partial pressure of O₂ and H₂O, in the range below1000 parts per million. Curing in an O₂ and H₂O ambient is one option toimprove the low k film mechanical properties, but it will increase the kvalue.

The UV light treatment step is performed utilizing a source that cangenerate light having a wavelength from about 500 to about 150 nm, toirradiate the substrate while the wafer temperature is maintained at upto 450° C., with temperatures from 200° C. −450° C. being preferred anda temperature from 350° C. to 425° C. being even more highly preferred.Radiation with >370 nm is of insufficient energy to dissociate oractivate important bonds, so the wavelength range 150-370 nm is apreferred range. Using literature data and absorbance spectra measuredon as deposited films, the inventors have found that <170 nm radiationmay not be favored due to degradation of the SiCOH film. Further, theenergy range 310-370 nm is less useful than the range 150-310 nm, due tothe relatively low energy per photon from 310-370 nm. Within the 150-310nm range, optimum overlap with the absorbance spectrum of the asdeposited film and minimum degradation of the film properties (such ashydrophobicity) may be optionally used to select a most effective regionof the UV spectrum for changing the SiCOH properties.

The UV light treatment step may be performed in an inert gas, a hydrogensource gas or a gas mixture of O₂ and H₂O using the partial pressurerange mentioned above.

The electron beam treatment step is performed utilizing a source that iscapable of generating a uniform electron flux over the wafer, withenergies from 0.5 to 25 keV and current densities from 0.1 to 100microAmp/cm² (preferably 1 to 5 microAmp/cm²), while the wafertemperature is maintained at a temperature up to 450° C., withtemperatures from 200°-450° C. being preferred, and temperature from350° to 425° being even more highly preferred. The preferred dose ofelectrons used in the electron beam treatment step is from 50 to 500microcoulombs/cm², with 100 to 300 microcoulombs/cm² range beingpreferred.

The electron beam treatment step may be performed in an inert gas, ahydrogen source gas or a gas mixture of O₂ and H₂O using the partialpressure range mentioned above.

The plasma treatment step is performed utilizing a source that iscapable of generating atomic hydrogen (H), and optionally CH₃ or otherhydrocarbon radicals. Downstream plasma sources are preferred overdirect plasma exposure. During plasma treatment the wafer temperature ismaintained at a temperature up to 450° C., with temperatures from 200°C.-450° C. being preferred and temperatures from 350° C. to 425° C.being more highly preferred.

The plasma treatment step is performed by introducing a gas into areactor that can generate a plasma and thereafter it is converted into aplasma. The gas that can be used for the plasma treatment includes inertgases such as Ar, N, He, Xe or Kr, with He being preferred; hydrogen orrelated sources of atomic hydrogen, methane, methylsilane, relatedsources of CH₃ groups, and mixtures thereof. The flow rate of the plasmatreatment gas may vary depending on the reactor system being used. Thechamber pressure can range anywhere from 0.05 to 20 torr, but thepreferred range of pressure operation is 1 to 10 torr. The plasmatreatment step occurs for a period of time, which is typically fromabout ½ to about 10 minutes, although longer times may be used withinthe invention.

An RF or microwave power source is typically used to generate the aboveplasma. The RF power source may operate at either a high frequency range(on the order of about 100 W or greater); a low frequency range (lessthan 250 W) or a combination thereof may be employed. The high frequencypower density can range anywhere from 0.1 to 2.0 W/cm² but the preferredrange of operation is 0.2 to 1.0 W/cm². The low frequency power densitycan range anywhere from 0.1 to 1.0 W/cm² but the preferred range ofoperation is 0.2 to 0.5 W/cm². The chosen power levels must be lowenough to avoid significant sputter etching of the exposed dielectricsurface (<5 nanometers removal).

In addition to the above, a deep ultra-violet (DUV) laser source canalso be employed to cause the dissociation of the porogen from the asdeposited dielectric film 12. The laser source used to treat thedeposited dielectric film 12 is typically an excimer laser whichoperates at one of several DUV wavelengths depending on the laser gasmixture. For example, a XeF laser which produces 308 nm radiation can beemployed. Also, a KrF laser that produces 248 nm radiation, or a ArFlaser that produces 193 nm radiation can be employed in the presentinvention. Excimer lasers can operate at several hundred pulses persecond with pulse energies up to a Joule (J) resulting in severalhundred Watt (W) output.

The laser employed in treating the as deposited dielectric film 12preferably operates under a pulse mode. The laser beam can be expandedto expose the entire sample. Alternatively, and for larger samples, thelaser exposure area can be raster scanned across the sample to provideuniform dose. Using excimer laser, the fluence is limited to less than 5mJ/cm² per pulse to ensure ablation will not occur. The short pulseduration of about 10 ns for the excimer laser can cause materialablation at fluence levels greater than 20 mJ/cm². Typically, laserfluence levels of 0.1-5 mJ/cm² per pulse are employed. The total dosecan vary from 1 to 10000 Joules/cm², preferably 500-2000 J/cm². This isachieved by multiple laser pulse exposure. For example, a dose of 1000J/cm² can be obtained using a fluence of 1 mJ/cm² for a duration of 10⁶pulses. Excimer laser normally operates at a few hundreds pulses persecond. Depending of the total dosage required, the overall exposuretime period for the DUV laser treatment for a several seconds to hours.A typical 500 J/cm² dose is achieved in less than 15 min using a 200 Hzlaser operating at a fluence level of 3 mJ/cm² per pulse.

Moreover, the SiCOH dielectric film is also characterized as havingbetween about 5 and about 40 atomic percent of Si; between about 5 andabout 45 atomic percent of C; between 0 and about 50 atomic percent ofO; and between about 10 and about 55 atomic percent of H. Thecompositional ranges of the atoms in the final film may be slightlybelow that of the as deposited film 12. The treated SiCOH dielectricfilm 14 also has other characteristics, e.g., a tri-bonded network,crack velocity in water (on the order of less than 10⁻¹² meters persecond), thermal stability above 350° C., etc, that are similar to theas deposited dielectric film 12.

As stated above, the treated SiCOH dielectric film of the presentinvention has a uniform atomic and structural composition throughout theentire film in both vertical and horizontal directions. Moreover, theinventive film, i.e., the treated SiCOH dielectric film 14 is morestable than conventional SiCOH films that are formed from twoprecursors.

The SiCOH dielectric film 14 has a controlled porosity having molecularscale voids (i.e., nanometer-sized pores) of between about 0.5 to about20 nanometers in diameter, and preferably from about 0.5 to about 5 nmin diameter. According to the invention, the molecular scale voidsoccupy a volume of between about 5% and about 60%. Also according to theinvention, the dielectric material of this invention contains molecularscale voids that are characterized by a pore size distribution and saidsize distribution has a maximum (in the distribution) between, 0.7 and 3nm, and preferably between, 0.7 and 2.5 nm.

In addition, the inventive SiCOH dielectric film 14 has improvedmechanical properties at the same values of dielectric constant. Forexample, for an inventive film having a thickness of about 1-2 μm thefollowing properties were measured: a low film stress (on the order ofabout 15-26 MPa), a low crack velocity (on the order of less than 1E-10m/sec), a modulus from about 3 to about 3.8 GPa, and a hardness fromabout 0.2 to about 0.24 GPa.

Table 1 shows physical properties for other SiCOH dielectric filmshaving the thickness mentioned in the table.

TABLE 1 Single Precursor SiCOH Film Evaluation Sample Crack ThicknessVelocity Modulus Hardness (μm) Stress (MPa) (m/sec) (GPa) (GPa) Comment1.1-1.3 26 +/− 5 5.6E−11 3.62 +/− 0.7 0.23 +/− 0.05 k = 2.52-2.6 1.25 26+/− 5  <1E−10 3.61 +/−0.12 0.23 +/− 0.01 k = 2.52-2.55; top 100 nm soft1.85 26 +/− 5  <1E−10 3.65 +/− 0.01 0.24 k = 2.52-2.55; top 100 nm soft1.88 26 +/− 5 <10E−10  3.78 +/− 0.11 0.23 +/− 0.01 k = 2.52-2.55 0.7-1.217 +/− 5 9.7E−11 3.34 +/− 0.08 0.20 +/− 0.006 k = 2.6 1.4-2.6 14 +/− 4 1.2E−10, 2.94 +/− 0.004 0.18 +/− 0.004 k = 2.6 no growth

The SiCOH dielectric film 14 of the present invention may be used as theinterlevel and/or intralevel dielectric, a capping layer, and/or as ahard mask/polish-stop layer in electronic structures.

The electronic structure of the present invention includes apre-processed semiconducting substrate that has a first region of metalembedded in a first layer of insulating material, a first region ofconductor embedded in a second layer of insulating material, the secondlayer of insulating material being in intimate contact with the firstlayer of insulating material, the first region of conductor being inelectrical communication with the first region of metal, and a secondregion of conductor being in electrical communication with the firstregion of conductor and being embedded in a third layer of insulatingmaterial, the third layer of insulating material being in intimatecontact with the second layer of insulating material.

In the above structure, each of the insulating layers can comprise theinventive SiCOH dielectric film 14.

The electronic structure may further include a dielectric cap layersituated in-between the first layer of insulating material and thesecond layer of insulating material, and may further include adielectric cap layer situated in-between the second layer of insulatingmaterial and the third layer of insulating material. The electronicstructure may further include a first dielectric cap layer between thesecond layer of insulating material and the third layer of insulatingmaterial, and a second dielectric cap layer on top of the third layer ofinsulating material.

The dielectric cap material can be selected from silicon oxide, siliconnitride, silicon oxynitride, silicon carbon nitride (SiCN), refractorymetal silicon nitride with the refractory metal being Ta, Zr, Hf or W,silicon carbide, silicon carbo-oxide, carbon doped oxides and theirhydrogenated or nitrided compounds. In some embodiments, the dielectriccap itself can comprise the inventive treated SiCOH dielectric material.The first and the second dielectric cap layers may be selected from thesame group of dielectric materials. The first layer of insulatingmaterial may be silicon oxide or silicon nitride or doped varieties ofthese materials, such as PSG or BPSG.

The electronic structure may further include a diffusion barrier layerof a dielectric material deposited on at least one of the second andthird layer of insulating material. The electronic structure may furtherinclude a dielectric layer on top of the second layer of insulatingmaterial for use as a RIE hard mask/polish-stop layer and a dielectricdiffusion barrier layer on top of the dielectric RIE hardmask/polish-stop layer. The electronic structure may further include afirst dielectric RIE hard mask/polish-stop layer on top of the secondlayer of insulating material, a first dielectric RIE diffusion barrierlayer on top of the first dielectric polish-stop layer a seconddielectric RIE hard mask/polish-stop layer on top of the third layer ofinsulating material, and a second dielectric diffusion barrier layer ontop of the second dielectric polish-stop layer. The dielectric RIE hardmask/polish-stop layer may be comprised of the inventive SiCOHdielectric material 14 as well.

The electronic devices which can contain the inventive treated SiCOHdielectric film are shown in FIGS. 2-5. It should be noted that thedevices shown in FIGS. 2-5 are merely illustrative examples of thepresent invention, while an infinite number of other devices may also beformed by the present invention novel methods.

In FIG. 2, an electronic device 30 built on a semiconductor substrate 32is shown. On top of the semiconductor substrate 32, an insulatingmaterial layer 34 is first formed with a first region of metal 36embedded therein. After a CMP process is conducted on the first regionof metal 36, a treated SiCOH dielectric film 38 of the present inventionis formed on top of the first layer of insulating material 34 and thefirst region of metal 36. The first layer of insulating material 34 maybe suitably formed of silicon oxide, silicon nitride, doped varieties ofthese materials, or any other suitable insulating materials. The treatedSiCOH dielectric film 38 is then patterned in a photolithography processfollowed by etching and a conductor layer 40 is deposited thereon. Aftera CMP process on the first conductor layer 40 is carried out, a secondlayer of the inventive treated SiCOH film 44 is deposited by a plasmaenhanced chemical vapor deposition process overlying the first treatedSiCOH dielectric film 38 and the first conductor layer 40. The conductorlayer 40 may be a deposit of a metallic material or a nonmetallicconductive material. For instance, a metallic material of aluminum orcopper, or a nonmetallic material of nitride or polysilicon. The firstconductor 40 is in electrical communication with the first region ofmetal 36.

A second region of conductor 50 is then formed after a photolithographicprocess on the treated SiCOH dielectric film 44, followed by etching andthen a deposition process for the second conductor material. The secondregion of conductor 50 may also be a deposit of either a metallicmaterial or a nonmetallic material, similar to that used in depositingthe first conductor layer 40. The second region of conductor 50 is inelectrical communication with the first region of conductor 40 and isembedded in the second layer of the treated SiCOH dielectric film 44.The second layer of the treated SiCOH dielectric film 44 is in intimatecontact with the first layer of the treated SiCOH dielectric material38. In this example, the first layer of the treated SiCOH dielectricfilm 38 is an intralevel dielectric material, while the second layer ofthe treated SiCOH dielectric film 44 is both an intralevel and aninterlevel dielectric.

FIG. 3 shows a present invention electronic device 60 similar to that ofelectronic device 30 shown in FIG. 2, but with an additional dielectriccap layer 62 deposited between the first insulating material layer 38and the second insulating material layer 44. The dielectric cap layer 62can be suitably formed of a material such as silicon oxide, siliconnitride, silicon oxynitride, refractory metal silicon nitride with therefractory metal being Ta, Zr, Hf or W, silicon carbide, siliconcarbo-nitride (SiCN), silicon carbo-oxide (SiCO), and their hydrogenatedcompounds. The additional dielectric cap layer 62 functions as adiffusion barrier layer for preventing diffusion of the first conductorlayer 40 into the second insulating material layer 44 or into the lowerlayers, especially into layers 34 and 32.

Another alternate embodiment of the present invention electronic device70 is shown in FIG. 4. In the electronic device 70, two additionaldielectric cap layers 72 and 74 which act as a RIE mask and CMP(chemical mechanical polishing) polish stop layer are used. The firstdielectric cap layer 72 is deposited on top of the first treated SiCOHdielectric material 38 and used as a RIE mask and CMP stop, so the firstconductor layer 40 and layer 72 are approximately co-planar after CMP.The function of the second dielectric layer 74 is similar to layer 72,however layer 74 is utilized in planarizing the second conductor layer50. The polish stop layer 74 can be a deposit of a suitable dielectricmaterial such as silicon oxide, silicon nitride, silicon oxynitride,refractory metal silicon nitride with the refractory metal being Ta, Zr,Hf or W, silicon carbide, silicon carbo-oxide (SiCO), and theirhydrogenated compounds. A preferred polish stop layer composition isSiCH or SiCOH for layers 72 or 74. When layer 72 is comprised of SiCOH,it is preferred that the inventive treated SiCOH film be employed. Asecond dielectric layer 74 can be added on top of the second treatedSiCOH dielectric film 44 for the same purposes.

Still another alternate embodiment of the present invention electronicdevice 80 is shown in FIG. 5. In this alternate embodiment, anadditional layer 82 of dielectric material is deposited and thusdividing the second insulating material layer 44 into two separatelayers 84 and 86. The intralevel and interlevel dielectric layer 44formed of the inventive treated SiCOH dielectric film, shown in FIG. 2,is therefore divided into an interlayer dielectric layer 84 and anintralevel dielectric layer 86 at the boundary between via 92 andinterconnect 94. An additional diffusion barrier layer 96 is furtherdeposited on top of the upper dielectric layer 74. The additionalbenefit provided by this alternate embodiment electronic structure 80 isthat dielectric layer 82 acts as an RIE etch stop providing superiorinterconnect depth control. Thus, the composition of layer 82 isselected to provide etch selectivity with respect to layer 86.

Still other alternate embodiments may include an electronic structurewhich has layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate which has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of the insulating material wherein the second layer ofinsulating material is in intimate contact with the first layer ofinsulating material, and the first region of conductor is in electricalcommunication with the first region of metal, a second region ofconductor in electrical communication with the first region of conductorand is embedded in a third layer of insulating material, wherein thethird layer of insulating material is in intimate contact with thesecond layer of insulating material, a first dielectric cap layerbetween the second layer of insulating material and the third layer ofinsulating material and a second dielectric cap layer on top of thethird layer of insulating material, wherein the first and the seconddielectric cap layers are formed of a material that includes theinventive SiCOH dielectric film.

Still other alternate embodiments of the present invention include anelectronic structure which has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure that includesa pre-processed semiconducting substrate that has a first region ofmetal embedded in a first layer of insulating material, a first regionof conductor embedded in a second layer of insulating material which isin intimate contact with the first layer of insulating material, thefirst region of conductor is in electrical communication with the firstregion of metal, a second region of conductor that is in electricalcommunication with the first region of conductor and is embedded in athird layer of insulating material, the third layer of insulatingmaterial is in intimate contact with the second layer of insulatingmaterial, and a diffusion barrier layer comprise the SiCOH film of thepresent invention formed on at least one of the second and third layersof insulating material.

Still other alternate embodiments include an electronic structure whichhas layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a reactive ion etching(RIE) hard mask/polish stop layer on top of the second layer ofinsulating material, and a diffusion barrier layer on top of the RIEhard mask/polish stop layer, wherein the RIE hard mask/polish stop layerand the diffusion barrier layer comprise the SiCOH dielectric film ofthe present invention.

Still other alternate embodiments include an electronic structure whichhas layers of insulating materials as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a first RIE hard mask,polish stop layer on top of the second layer of insulating material, afirst diffusion barrier layer on top of the first RIE hard mask/polishstop layer, a second RIE hard mask/polish stop layer on top of the thirdlayer of insulating material, and a second diffusion barrier layer ontop of the second RIE hard mask/polish stop layer, wherein the RIE hardmask/polish stop layers and the diffusion barrier layers comprise thetreated SiCOH dielectric film of the present invention.

Still other alternate embodiments of the present invention includes anelectronic structure that has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure similar tothat described immediately above but further includes a dielectric caplayer which comprises the treated SiCOH dielectric material of thepresent invention situated between an interlevel dielectric layer and anintralevel dielectric layer.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A method of forming a dielectric film comprising: positioning asubstrate in a plasma enhanced chemical vapor deposition (PECVD)reactor; providing a single organosilicon precursor with a built-inorganic porogen into said PECVD reactor in the absence of anotherporogen source, said single organosilicon precursor with a built-inorganic porogen is selected from the group consisting ofvinylmethyldiethoxysilane, vinyltriethoxysilane,vinyldimethylethoxysilane, hexavinyldisiloxane, trivinylmethoxysilane,trivinylethoxysilane, vinylmethylethoxysilane,vinylmethyldiethoxysilane, vinylmethyldimethoxysilane,vinylpentamethyldisiloxane, vinyltetramethyldisiloxane, andvinyltrimethoxysilane; forming an as-deposited film from said singleorgansilicon precursor on said substrate, said as-deposited filmcomprising a SiCOH matrix component and an organic porogen component;and performing a treatment step that substantially removes said organicporogen component from said as-deposited film, said treatment stepconducted in the presence of an atmosphere selected from the groupconsisting of an inert gas and a hydrogen source and an inert gas,oxygen and water, thereby providing a porous SiCOH dielectric materialhaving a dielectric constant of about 2.7 or lower, said SiCOHdielectric material having a covalently bonded tri-dimensional networkstructure, a controlled porosity having molecular scale voids of betweenabout 0.5 to about 20 nanometers in diameter, said molecular scale voidsoccupying a volume of between about 5% and about 60%, a crack velocityin water on the order of less than 10⁻¹⁰ meters per second and isthermally stable above 350° C.
 2. The method of claim 1 furthercomprising mixing an inert gas with said single organosilicon precursorwith a built-in porogen.
 3. The method of claim 1 further comprisingmixing an oxidizing agent with said single organosilicon precursor witha built-in porogen.
 4. The method of claim 1 wherein said substrate is asemiconducting material, an insulating material, a conductive materialor a combination, including multilayers, thereof.
 5. The method of claim1 wherein said SiCOH matrix component and said organic porogen componentare covalently bonded.
 6. The method of claim 5 wherein said treatmentstep comprises selecting an energy source that is capable ofdissociating said organic porogen component from said SiCOH matrixcomponent, wherein said energy source comprises thermal, electron beam,plasma, UV, DUV or laser.
 7. The method of claim 6 wherein said energysource is thermal and said thermal source is capable of providing atemperature up to 450° C.
 8. The method of claim 7 wherein said thermalenergy source is an annealing process that is performed in the presenceof an inert gas and a hydrogen source.
 9. The method of claim 7 whereinsaid thermal energy source is an annealing process that is conducted inthe presence of an atmosphere that is an inert gas, oxygen and waterwherein the partial pressure of O₂ and H₂O are below 1000 ppm.
 10. Themethod of claim 6 wherein said energy source comprises UV or DUV lightthat can generate light having a wavelength from about 500 to about 150nm.
 11. The method of claim 6 wherein said energy source comprises a UVor DUV light treatment conducted in the presence of said inert gas andhydrogen source.
 12. The method of claim 6 wherein said energy source isa UV light treatment conducted in the presence of an inert gas, oxygenand water atmosphere wherein the partial pressure of O₂ and H₂O arebelow 1000 ppm.
 13. The method of claim 1 wherein said steps areincorporated within a process for fabricating an interconnect structurein an electronic device.
 14. The method of claim 1 wherein said hydrogensource is hydrogen or a hydrocarbon.
 15. The method of claim 1 whereinthe built-in organic porogen present in the single organosiliconprecursor is a silicon-containing component.
 16. A method of forming adielectric film comprising: positioning a substrate in a plasma enhancedchemical vapor deposition (PECVD) reactor; providing a singleorganosilicon precursor including a silicon containing organic porogeninto said PECVD reactor, said single organosilicon precursor with abuilt-in organic porogen comprising a silane derivative having themolecular formula SiRR¹R²R³, a disiloxane derivative having themolecular formula R⁴R⁵R⁶—Si—O—Si—R⁷R⁸R⁹, or a trisiloxane derivativehaving the molecular formula R¹⁰R¹¹R¹²—Si—O—Si—R¹³R¹⁴—O—Si—R¹⁵R¹⁶R¹⁷where R and R¹⁻¹⁷ may or may not be identical and are selected from H,alkyl, alkoxy, epoxy, phenyl, vinyl, allyl, alkenyl or alkynyl groupsthat may be linear, branched, cyclic, polycyclic and may befunctionalized with oxygen, nitrogen or fluorine containingsubstituents; forming an as-deposited film from said single organsiliconprecursor on said substrate, said as deposited film comprising a SiCOHmatrix component and an organic porogen component; and performing atreatment step that substantially removes said organic porogen componentfrom said as deposited film thereby providing a SiCOH dielectricmaterial having a dielectric constant of about 2.7 or lower.